From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-23.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 94F53C433DB for ; Mon, 15 Mar 2021 15:16:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 69D4764E33 for ; Mon, 15 Mar 2021 15:16:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231452AbhCOPQD (ORCPT ); Mon, 15 Mar 2021 11:16:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60974 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231604AbhCOPPc (ORCPT ); Mon, 15 Mar 2021 11:15:32 -0400 Received: from mail-pj1-x102e.google.com (mail-pj1-x102e.google.com [IPv6:2607:f8b0:4864:20::102e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 84A46C06174A for ; Mon, 15 Mar 2021 08:15:32 -0700 (PDT) Received: by mail-pj1-x102e.google.com with SMTP id lr1-20020a17090b4b81b02900ea0a3f38c1so2105480pjb.0 for ; Mon, 15 Mar 2021 08:15:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=29tlbpBidLiX7cZGeLgeOwEsi9aLcqGPG2CxmfByAsQ=; b=G70Yi+HZ7xQs8CVYSesF7lAmPjStzjs1y2vz86ytp/moWZPMOjyu5kDS2vRMASm7TC eYkptyylr9YmpYCXc541zduhUa5bjGaDikfNvXgW25K/aivRZmB3DxnwTgEyEM5+SNcG 4y2RYGB60pM6GWjqf8yyr1JodFbkJZBROVT+PNIPtRN1iFin52czM+TWVuKISmfa5KZU kN4FWw3MA1dFnVAdFpXnaPaA0gYhmSnhQqoec3l38kyI7WxlVJq6gKB4YstXw20q9npo og7Soan1r30+kXGpZXXShyJOdwelsknDbjsfxtnd/1GokjN46GBlgD5/2c5Q1r7cOz4n XjIA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=29tlbpBidLiX7cZGeLgeOwEsi9aLcqGPG2CxmfByAsQ=; b=JJ5aQS9M6eUTX1HGOJn3o5i3k9+ms2689rGtEMOWURFmczPNEggXfbwSAJ3jJUXhw2 oM0qduhvHWxd7b7fCttGJZlqIT+IzGF34qXZbw4TEQAjjVwDcnoW+Eb3kz9wNgRzX8TT 9mGB3cOCOG0R/OhdW2yr3a4ZLWMVz8nFUSSl8yICNg7U3jldojVSOyHznDuKRTCuUxjb DCqNb7fXLpZGI+SBbS3cfdYI4dreE4ykGb96FP3fD8+aQvV6qB1p2dH25QsW+D0+/ouO ZLUUdkQChvPLxIlSSycwBWc9hEVxAghBBQc41z2ychrIMswh6UnyyEAz4YWUCs/8wRuO supA== X-Gm-Message-State: AOAM533LiYZr4o6G9/z3p9/pmJJZ3MQONuoF0WW7GDJUZmroTIsgyVtg zqFAWsE6T98QWr5DqpzZvLBJSQ== X-Google-Smtp-Source: ABdhPJw0Wp2wjRR9CitnPrjcB1f6eX+nzwALcNAzjhks9pfylM6xEeSY/z9JaS56JUgekOlamOBRbA== X-Received: by 2002:a17:902:c154:b029:e5:e7cf:9627 with SMTP id 20-20020a170902c154b02900e5e7cf9627mr11785530plj.68.1615821331929; Mon, 15 Mar 2021 08:15:31 -0700 (PDT) Received: from google.com ([2620:15c:f:10:3d60:4c70:d756:da57]) by smtp.gmail.com with ESMTPSA id h14sm11725077pjc.37.2021.03.15.08.15.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 15 Mar 2021 08:15:31 -0700 (PDT) Date: Mon, 15 Mar 2021 08:15:24 -0700 From: Sean Christopherson To: Vitaly Kuznetsov Cc: kvm@vger.kernel.org, Paolo Bonzini , Wanpeng Li , Jim Mattson , Marcelo Tosatti Subject: Re: [PATCH 3/4] KVM: x86: hyper-v: Track Hyper-V TSC page status Message-ID: References: <20210315143706.859293-1-vkuznets@redhat.com> <20210315143706.859293-4-vkuznets@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210315143706.859293-4-vkuznets@redhat.com> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Mon, Mar 15, 2021, Vitaly Kuznetsov wrote: > Create an infrastructure for tracking Hyper-V TSC page status, i.e. if it > was updated from guest/host side or if we've failed to set it up (because > e.g. guest wrote some garbage to HV_X64_MSR_REFERENCE_TSC) and there's no > need to retry. > > Also, in a hypothetical situation when we are in 'always catchup' mode for > TSC we can now avoid contending 'hv->hv_lock' on every guest enter by > setting the state to HV_TSC_PAGE_BROKEN after compute_tsc_page_parameters() > returns false. > > Signed-off-by: Vitaly Kuznetsov > --- > diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c > index eefb85b86fe8..2a8d078b16cb 100644 > --- a/arch/x86/kvm/hyperv.c > +++ b/arch/x86/kvm/hyperv.c > @@ -1087,7 +1087,7 @@ void kvm_hv_setup_tsc_page(struct kvm *kvm, > BUILD_BUG_ON(sizeof(tsc_seq) != sizeof(hv->tsc_ref.tsc_sequence)); > BUILD_BUG_ON(offsetof(struct ms_hyperv_tsc_page, tsc_sequence) != 0); > > - if (!(hv->hv_tsc_page & HV_X64_MSR_TSC_REFERENCE_ENABLE)) > + if (hv->hv_tsc_page_status == HV_TSC_PAGE_BROKEN) > return; > > mutex_lock(&hv->hv_lock); ... > @@ -1133,6 +1133,12 @@ void kvm_hv_setup_tsc_page(struct kvm *kvm, > hv->tsc_ref.tsc_sequence = tsc_seq; > kvm_write_guest(kvm, gfn_to_gpa(gfn), > &hv->tsc_ref, sizeof(hv->tsc_ref.tsc_sequence)); > + > + hv->hv_tsc_page_status = HV_TSC_PAGE_SET; > + goto out_unlock; > + > +out_err: > + hv->hv_tsc_page_status = HV_TSC_PAGE_BROKEN; > out_unlock: > mutex_unlock(&hv->hv_lock); > } > @@ -1193,8 +1199,13 @@ static int kvm_hv_set_msr_pw(struct kvm_vcpu *vcpu, u32 msr, u64 data, > } > case HV_X64_MSR_REFERENCE_TSC: > hv->hv_tsc_page = data; > - if (hv->hv_tsc_page & HV_X64_MSR_TSC_REFERENCE_ENABLE) > + if (hv->hv_tsc_page & HV_X64_MSR_TSC_REFERENCE_ENABLE) { > + if (!host) > + hv->hv_tsc_page_status = HV_TSC_PAGE_GUEST_CHANGED; > + else > + hv->hv_tsc_page_status = HV_TSC_PAGE_HOST_CHANGED; Writing the status without taking hv->hv_lock could cause the update to be lost, e.g. if a different vCPU fails kvm_hv_setup_tsc_page() at the same time, its write to set status to HV_TSC_PAGE_BROKEN would race with this write. > kvm_make_request(KVM_REQ_MASTERCLOCK_UPDATE, vcpu); > + } > break; > case HV_X64_MSR_CRASH_P0 ... HV_X64_MSR_CRASH_P4: > return kvm_hv_msr_set_crash_data(kvm, > -- > 2.30.2 >